Communication systems and air interface protocols that utilize or rely on OFDM modulation and signals are known and becoming more popular, particularly in systems with narrow bandwidth or multipath channels. OFDM signals employ a multitude of closely frequency spaced subcarriers where the creation of these subcarriers result in orthogonal subcarriers with relatively slower symbol rates on each carrier. OFDM modulation provides increased capacity in many situations, provided a receiver for the OFDM signals is a coherent receiver. A coherent receiver is a receiver that can be accurately synchronized in time and frequency with the transmitter, i.e., synchronized with the transmitted signal. This synchronization is required in order to maintain the orthogonality of the various subcarriers. The sensitivities of inter symbol and inter carrier interference to a lack of synchronization can be relatively large.
Various approaches are known for obtaining synchronization and most approaches initially use a course synchronization procedure that essentially provides frame synchronization and course frequency synchronization, e.g., within one subcarrier frequency spacing. After course synchronization has been acquired, various algorithms are utilized to further (fine) synchronize (in time and frequency) the receiver to the transmitted and thus received signal. The known approaches result in an interference floor for inter carrier or inter symbol interference (ICI, ISI) that may not be low enough for systems with large numbers of subcarriers or particularly complex channels (rapid fading, etc.). Furthermore, implementing known approaches typically require non-trivial amounts of processing resources. Thus new approaches for fine synchronization that offer significant improvements in performance with limited processing resources are desirable.